With the demand for alternative fueled, environmentally friendly or “green” vehicles are on the rise, electric vehicles and will become the vehicles of choice because of their zero emissions and their efficiency. Each electric vehicle may require a large amount of power to recharge. Many electric vehicle prototypes as of this writing have a storage capacity of 35 kWh or greater. Each electric vehicle may require a recharge within a limited period of time, most likely overnight. In addition, batteries may supply power back into the grid during certain conditions and this interaction must be controlled as well as the charging activities.
As more and more electric vehicles come on line for being charged, this could cause a tremendous strain on existing power grids even if most charging of electric vehicles occurs in off peak hours. The EV load during charging or discharging could approach 75 Amps per vehicle. This level of current draw could overload existing distribution transformers if several vehicles attempt to charge simultaneously in conjunction with other normal loads on the transformer like HVAC etc. Increasing the size of existing transformers to meet this potential demand could prove to be very costly. Also, simultaneous charging across the entire grid could cause overloads higher on feeders or substations higher in the grid hierarchy.
As mentioned, this potentially large electric vehicle charging load would add to the present load on the distribution system. A large contributor to the present load on the electric power distribution system is Heating Ventilation and Air Conditioning (HVAC) systems in addition to other large appliances like electric clothes dryers and electric ranges.
A focus of upgrades to the electric grids could include distribution transformers. Distribution transformers are generally positioned in proximity of homes, which will also house any electric vehicles. Each transformer usually has a limited amount of supply current for charging large loads, like electric vehicles.
Currently, some solutions exist which manage the additional load that electric vehicles may place on existing power grids. FIG. 1 illustrates one such prior art solution.
FIG. 1 illustrates a prior art power grid system 10 that can include a central controller 12, a substation 14, a feeder 16, a distribution transformer 18, and electric vehicle chargers 20. The central controller 12 can be coupled to the substations 14 which are in turn coupled to feeders 16. The feeders 16 may be coupled to distribution transformers 18. The distribution transformers 18 can be coupled to and support various electric vehicle chargers 20.
The power grid system 10 functions as a power distribution system/network that connects producers of power with consumers of power. The power grid system 10 may include, but is not limited to, any one of generators, transformers, interconnects, switching stations, and safety equipment. As illustrated in prior art FIG. 1, a central controller 12 can service at least two different substations 14A, 14B. The central controller 12 can be designed to manage the extra demand or additional load that can be attributed to the numerous electric vehicle chargers 20 that can be brought online to support the battery storage of numerous electric vehicles.
One of the main problems of this prior art central controller 12 model is that it will require tremendous computing power to manage all of the variables associated with the charging of electric vehicles from a central location. If there are any problems with the central controller 12, such problems could directly impact numerous customers with electric vehicles. In addition to this system 10 having a single point of critical failure, this central controller 12 may require additional infrastructure behind the power grid system 10 itself so that the central controller 12 can communicate with each electric vehicle charger 20. For example, the central controller 12 may require an Internet connection or a wireless network connection in order to communicate with the electric vehicle chargers 20. This is on top of the communications infrastructure needed by the central controller 12 to communicate with monitoring points on the substations 14 and the feeders 16.
Accordingly, there is a need in the art for a system and method that can locally and autonomously manage the demand or load presented by electric vehicles and which does not require significant additional communications infrastructure. There is a need in the art to eliminate single point of failure designs so that groups of electric vehicle chargers may operate independently of one another. Also, such a solution, operating at the transformer level could offer control at the feeder and substation level as well.